The invention relates to an axle journal (steering knuckle) or wheel mount comprising an aluminum body, a wheel bearing unit, and a steel pivot, and a method of producing an axle journal or wheel mount.
On their front axles, rear-wheel drive vehicles have axle journals that each support the steerable wheel and are pivotable around a steering knuckle pin.
In the prior art, rear-wheel drive vehicles usually have on their front axle steel-forged axle journals with pivots. The pivots each serve to receive a wheel bearing, the wheel hub, brake disk and finally the actual wheel.
On their rear axle, front-wheel drive vehicles comprise a wheel mount in which either a steel pivot is integrated to receive the wheel bearing or on which the wheel bearing as a unit is directly screwed.
The advantage of steel-forged axle journals or wheel mounts with pivots lies in the very high mechanical strength properties, such as very high yield points. The disadvantage of steel-forged axle journals or wheel mounts with pivots does, however, lie in the fact that these components are relatively heavy and hence stand in the way of efforts to reduce the weight of automobiles in particular.
To reduce the weight of the axle journals or wheel mounts, aluminum axle journals produced by chill casting were developed. A wheel bearing is screwed on the aluminum casting. In terms of the outer shape, the aluminum axle journals or wheel mounts clearly differ from the steel-forged axle journals. The aluminum axle journals or wheel mounts do not have any integrated aluminum pivots because an aluminum pivot is unable to transfer the forces and moments transferred from the wheel via the wheel bearings. A comparison of the moduli of elasticity of steel and aluminum reveals the high elasticity of aluminum. Nevertheless, to achieve a desirable strength, the wheel bearing on the aluminum casting has to be attached to a point at which the aluminum casting is sufficiently dimensioned to transfer reliably the emergent forces and moments. This does, however, result in a wheel bearing unit that has a large internal diameter, on account of which this wheel bearing unit entails considerable expense. Furthermore, the weight saving obtained by using an aluminum casting is again largely offset by the heavy wheel bearing unit.